This invention relates to cylindrical seal members such as valve plugs, pistons or the like which are received within a cylindrical chamber for sliding or rotary movement within the chamber. In particular, the invention relates to such cylindrical seal members which are provided with a novel seal mechanism for making a fluid seal between the cylindrical member and the chamber.
Apparatus and processes for automatically filling containers such as cans with both food and non-food products have become very sophisticated. Such apparatus and processes are used to fill containers with liquid, semi-liquid, pasty or solid products including both food products such as liver paste, baby foods, jellies, vegetable oil, mustard, sauces, etc., and non-foods such as mineral oil, wax, paints, etc. The apparatus used may take a variety of form, one of the most popular being the so-called rotary piston filler, such as the MR 16, MR 22, and MR 30 units manufactured by Hema International, Inc. of Utah.
Rotary fillers typically include a generally cylindrical hopper made, for example, of stainless steel, a number of filling assemblies spaced apart about the exterior of the hopper, and a container or can conveying system for moving cans into position underneath the filling assemblies to receive product. The filling assemblies each typically includes a vertically disposed cylinder, a valve coupling the lower end of the cylinder to the hopper and operable to either allow material to flow from the hopper into the cylinder or to flow from the cylinder into a can positioned below the valve, and a piston movable in the cylinder to force material from the cylinder into the can. Rotary fillers also typically include a piston support structure for causing the pistons to move upwardly in the cylinders when product is flowing from the hopper into the cylinders, and downwardly when product is being forced from the cylinder into cans. A typical rotary filler is shown and described in U.S. Pat. No. 4,501,622, issued on Feb. 26, 1985 to the inventor of the present invention.
Of particular interest to the present invention are cylindrical seal members which take the form of pistons and valves used in rotary filler apparatus. Although the cylindrical seal members can be used in a variety of diverse applications, the present disclosure will describe the novel seal members in relation to pistons and valves as used in typical rotary filler apparatus. Of course, the invention is not intended to be, nor should it be, construed to be limited to the illustrative disclosure. Instead, the scope of the invention, as set forth in the appended claims, is intended to cover improved cylindrical seal members which can be used in a variety of diverse applications.
Pistons and rotary valves which utilize conventional o-rings as a seal have presented problems, especially in the rotary filler apparatus used in packaging of food. It is difficult to keep food from leaking or escaping behind the o-rings. Multiple o-rings are generally required to alleviate the problems of leakage about the o-rings in both piston and rotary valves and to provide proper sealing of pistons to develop adequate suction when the piston is used to draw food from the hopper to the cylinder prior to discharge of the food into a can positioned beneath the cylinder.
The prior pistons and valves utilizing o-ring seals also present a problem during cleaning. Automatic means have been recently proposed (see U.S. Pat. No. 4,502,622) for cleaning the rotary feeders used in food applications. The o-ring seals on pistons and valves are difficult to clean properly except by hand. The o-rings have to be removed so that the retainer grooves and the o-rings can be adequately cleaned. This is very cumbersome and at least partially obviates the advantages of the automatic cleaning means and methods. The o-rings and grooves, if not cleaned often and thoroughly, collect food and provide an excellent habitat for bacteria growth.
As can be recognized, it is highly desirable to develop an improved cylindrical seal member which can be used in the form of pistons and rotary valves on rotary feeder apparauus. Such cylindrical seal members would eliminate the use of conventional o-rings while being adapted to be easily cleaned with automatic cleaning methods which have been proposed and are now coming into use in the food packaging industry.